Hydraulic brake booster



March 9, 1937. E, MART N 2,073,163

HYDRAULIC BRAKE BOOSTER Filed March 8, 1955 2 Sheets-Sheet 1 March 9, 1937. G E -rm 2,073,163

HYDRAULIC BRAKE BOOSTER Filed March 8, 1935 2 Sheets-Sheet 2 Patented Mar. 9, 193? UNITED STATES 2,073,163 nrnaamc BRAKE noos'raa George E. Martin, Detroit, Mich., auignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application March 8, 1935, Serial No. 9,925

4 Claims.

This invention relates to brakes for vehicles. It has been proposed to arbitrarily divide unequally and in a predetermined ratio the braking forces functioning to retard the rotation of the front wheels and rear .wheels respectively. It has been proposed to make that differentiation proportional to the load supported by said front and rear wheels. It is known, however, that under the influence of deceleration there is a shifting of the load from the rear supporting wheels to the front wheels.

It is an object of this invention to provide braking for front and rear in a predetermined ratio, half on each, for example, and automatically to supplement the braking force applied to the front wheels in response to the above described change in loading.

A further object is to provide said supplemental braking by an inertia responsive vacuum servo 2o mechanism.

Other objects and advantages will be understood from the following description.

In the drawings accompanying this description, Fig. l is a top plan view of an embodiment of the invention applied to a vehicle.

Fig. 2 is a top plan view, partly in section, of

a double master cylinder.

Fig. 3 is a section on line 3-3 of Fig. 2.

Fig. 4 is a section on line 4-4 of Fig. 2.

Fig. 5 is a section on line 5-5 of Fig. 1.

Fig. 6 is a section on line 6-6 of Fig. 5.

Fig. '1 is a view in elevation, partly in section, of the power cylinder.

Fig. 8 is a diagrammatic view of a modification.

Referring to the drawings, I I represents a longitudinal member constituting a part of a vehicle chassis and I3 is a transverse member. is shown the engine for driving the vehicle. The

front wheels are marked I1 and the rear wheels I9. Each wheel has a brake drum 2I. A system of hydraulic conduits 23 connect wheel cylinders (not shown) within the drums of the front wheels with a master cylinder 25. A system of conduits 21 connectsa master cylinder 29 with wheel cylinders (not shown) within the drums of the rear wheels. Within the master cylinders are pistons 3I restoring springs 53 and the pistons are actuated by rods 33 with dust protectors 34. The

outer ends of the rods are pivoted by pins 35 to the forked ends 31 of an equalizer bar 39. This bar is pivoted at an intermediate point 4| to a rod 43 connected to a lever or pedal 45. The pedal pressure is equally distributed in the form shown, owing to the location of point 4I midway At I5 between the ends of bar 39, to the two rods and pistons, thereby applying equal pressures on the fluid columns leading to the front and rear wheel cylinders. Thus, when the load is distributed equally, the pressures to effect deceleration are equal.

The cylinders 25 and 29 are located within a casting 43 as shown by Figs. 2 and 4. This casting is secured in any convenient way to chassis bar II as shown by Fig. 1. This bar II also has an arm 46 to guide rod 43. The casting 43 has a reservoir chamber 41 above the cylinders 25, 29 and communicating passages 49 and 5|. The reservoir and passages are conventional expedients in hydraulic brake systems and need no explanation.

An arm 55 is formed on the side of the casting 43 remote from chassis bar II. It pivots a lever 51 at 59. The arm 6| of lever 51 is forked at 63 andengages a head 65 on the rod 33 associated with the piston of cylinder 25. The other arm 66 of lever 51 is pivoted at 01 to the end of a rod 69 extending into the head H of a power cylinder 13. The power cylinder has a piston 15 carrying a cup washer 11 secured by fastening means 13. The rod 63 is secured to the piston by nuts 8| and 83. The piston is biased to the position shown in the drawings by a spring 85. The cylinder has an opening 81 in the head 1I and an opening in the integral closed end 69. A conduit 9| is connected to the cylinder at opening 00 by suitable means 33. The cylinder is anchored to bar I3 by a suitable anchorage including a clip 35 secured at 31 to bar I3, and a fitting IOI secured to the cylinder. The parts 05 and IOI are pivoted together-at 33. Thefittlng engages the cylinder end and has threaded engagement with a fasten-' ingdevice I03 having a head I05 within the cylinder and stem with threads projecting through the wall. The pipe 9| is connected to a valve cylinder I01 also supported on bar l3. From the cylinder I01 and diametrically opposite the opening from pipe 9| is an opening for a pipe I09 connected at its other end to the manifold II I of en gine I5. A valve H3 is reciprocable within cylinder I01. It has a peripheral groove I I6 such that in one position of the valve registration is afforded between the conduits 9| and I09. The groove is normally displaced as in Fig. 5 at which time there is no communication between conduits 9| and I09 but pipe BI is able to vent the power cylinder by means of a recess II5 out in the valve. This position is normally maintained by a weighted inertia lever II1 pivoted at II9 to an arm I2I extending from frame bar I3. The upper end of lever H1 is pivoted at I23 to the outer end of valve I 13, there being a slot at the pivot to provide for the arc of movement of the lever.

The operation is as follows: Depression of pedal 45 presses upon the rod 43', which pressure is divided equally, in the form shown, between the two master cylinders 25 and 21 of the hydraulic brake applying means. When the brakes are so applied deceleration tends to shift some added load to the front wheel supporting means. For best results some added braking should be applied to the front wheel brakes. While at rest or when traveling at a uniform rate, the valve H5 is in the position shown in Fig. '5. Under those conditions there is no communication between pipes 95 and I09 and also the power cylinder 13 is vented through pipe 9| and the recess 1 l5. When deceleration occurs the inertia responsive weighted lever swings and causes the groove Hi to effect registration between pipes SI and i 09, and cuts off the communication between pipe 9! and the air. The manifold suction then serves to withdraw air from the power cylinder to the left of the piston 15. The air pressure on the right side causes the piston to move to the left. This movement operates through rod 59 and lever 51 to impress an added force on piston rod 33 and piston SI of the front wheel master cylinder. The added pressure is therefore applied to the braking system at the point of support then carrying the greater load. Restoration of the lever H! cuts off the vacuum servo and vents the cylinder.

The expedient is adaptable for mechanical braking as shown in Fig. 8. Here the pedal 45' may be used. It may operate through the equalizer 39'. The equalizer in this case is connected by rods 2M and 203 with arms 205 and 201 on rock shafts 209 and 2H. Arms 2i3, 215 on rock shaft 200 operate front brakes by means of links 2H, 2". Arms 22l, 223 on rock shaft 2 operate rear brakes by links 225, 221. Cross frame bar I! is the same as cross bar ll of Fig. 5 and the valve mechanism and inertia lever mounted on it are also the same. The power cylinder 13 is the same. Its rod 220 is connected to an arm 23l on rock shaft 208 of the front brake system. In this form the brakes are applied mechanically and equally by pedal depression and the vacuum servo supplements the front wheel brake application in an obvious manner.

I claim:

1. In a vehicle, supporting means at the rear, supporting means at the front, braking means associated with each supporting means, mechanism to apply the front and rear braking means in a predetermined ratio, power means, operable in response to the deceleration produced by the action of said braking means, to supplement the total braking force by adding to the force applied to the braking means associated with the front supporting means.

2. The invention defined by claim 1, said mechanism including hydraulic movable columns.

3. The invention defined by claim 1, said mechanism including hydraulic movable columns and said power means including a vacuum servo device comprising a power cylinder and an inertia controlled valve therefor.

4. In a hydraulic brake system for vehicles, front wheel braking means, rear wheel braking means, a plurality of master cylinders, conduit means from each master cylinder to one only of said braking means, means to apply all said braking means through the joint action of said master cylinders, power means to supplement said braking action, said power means comprising a source of fluid pressure, a valve, a power cylinder, said power cylinder operable upon the master cylinder for the front wheel braking means only and an inertia responsive weight operable to move said valve under the influence of the deceleration produced by said first mentioned braking.

GEORGE E. MARTIN. 

